In situations where a patient requires intermittent infusion or continuous slow introduction of a medicament, such as an antibiotic, into his or her system, the usual delivery modes involve gravity flow or a flow control infusion pump. These delivery modes have limitations for patients that can be ambulatory. For gravity flow, the patient is incapacitated or tied down to an IV pole from which the bag or bags of medicament are hung during the entire infusion process which may last a matter of hours. Known infusion pumps tend to be heavy, expensive and require a power source. In a nutshell, all of the aforesaid delivery modes are very limiting in lifestyle for the patient.
Ambulatory infusion devices which have been tried include various types of pneumatic, spring powered or portable electronic pump devices. Inasmuch as a goodly number of patients requiring such medicament infusion are either aged, in a weakened condition, or, conversely, desirous of being highly mobile, such attempts have not been successful due to the bulk, weight, cost and the reliability of such devices.
Previous ambulatory attempts are disclosed for example in U.S. Pat. No. 3,640,277, which includes a pneumatic system having a complex mechanical valving system. U.S. Pat. No. 3,153,414 requires constant monitoring of the bulb-pumped pressure. U.S. Pat. No. 4,507,116 is a pneumatic system which includes an elastic accumulator and diaphragm which reduces driving fluid pressure resulting in inconsistent flow rate.